The first time around, in warm, late August, the entire supply of gelato-stuffed doughnuts — about 300 preordered, and 600 more made to order — sold out in under two hours, said James Gray, managing partner of Glazed and Infused.

Gray took 700 preorders for this latest sale, after twice extending the deadline to order. He expects to double the number of sandwiches made on the spot at each Black Dog store.

There will be two lines — one for those who've ordered ahead, and one for those who like to take chances and don't mind waiting in the cold. Advance orders will be packaged, frozen and ready to take home.

"We learned our lesson from last time, to be a little more organized," Gray said.

The four varieties from which to choose are a pumpkin doughnut with Irish cream gelato; red velvet doughnut with cajeta (goat's milk caramel) gelato; apple doughnut with chai spice gelato; and a maple-bacon long john with banana bread gelato. The last is $8; the others are $6.

"They're really for sharing," Gray said.

Gray, who lives near the Black Dog shop in Ukrainian Village, pitched the idea of a gelato-doughnut mashup to Black Dog owner Jessica Oloroso in early summer.

"I've been enjoying her gelato for years, and I remember being in there and thinking, 'Oh man, I gotta put this on a doughnut.' And when I said it aloud, I said, 'Wait, that's a good idea,'" Gray said.

River North doughnut shop Firecakes offers its own version on its late-night menu: a honey-glazed square doughnut filled with housemade vanilla ice cream.

Gray and Oloroso have not yet decided whether to continue offering their desserts on a limited basis or more frequently.

"What we know is that we love the collaboration," Gray said.

Black Dog fans should know that, unlike last winter, Oloroso's shops will stay open through the cold months this year. Winter hours are 2-10 p.m. Fridays to Sundays.